Add storage-rent budget pre-flight check on create_market to prevent under-funded archives

[greatest0fallt1me]

Description

create_market does not pre-flight check that the caller has paid sufficient rent for the persistent-tier keys it will allocate. Add a pre-flight estimate and reject if insufficient.

Requirements and Context

• Compute rent estimate from StorageConfig constants and number of keys allocated
• Compare to env.storage().instance().get_ttl() headroom
• Reject with Error::InsufficientStorageRent
• Must be secure, tested, and documented
• Should be efficient and easy to review

Suggested Execution

1. Fork the repo and create a branch

   git checkout -b feat/create-market-rent-preflight

2. Implement changes
   • contracts/predictify-hybrid/src/markets.rs
   • contracts/predictify-hybrid/src/storage.rs
   • contracts/predictify-hybrid/src/err.rs
3. Test and commit
   • cargo test -p predictify-hybrid market_creation_validation_tests -- --nocapture
   • Cover edge cases: ample headroom, just-enough, insufficient
   • Include test output and notes in the PR

Example commit message

feat: pre-flight storage-rent check in create_market

Acceptance Criteria

• Rejection on insufficient rent
• Estimate formula documented
• No unwrap() introduced
• Tests cover boundary

Guidelines

• Avoid double-counting persistent-key bumps
• Minimum 95% coverage
• Clear documentation and inline comments
• Timeframe: 96 hours

[Songu3020]

@Songu3020 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hello, I’m a full stack developer with hands-on experience building with variety of tools including Nextjs, nodejs, nestjs, React, Typescript and more

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[grantfox-oss]

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Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #634)
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